The present invention relates generally to an electronic circuit for conditioning a direct current input signal and more particularly to such a circuit for conditioning a single direct current input signal or conditioning the difference between two direct current input signals.
It has been a known practice to couple various sensors to current transmitters to deliver a control signal or indicator signal typically utilized in some system control. For example, temperature and humidity sensors have typically been coupled to transmitters having an output range from 4 to 20 mA. Occasionally, instruments and process controllers adapted to receive such a signal require that such a signal be shifted and/or expanded or reduced in range. In the past in order to solve this problem specially designed transmitters have been utilized. In addition, in certain applications, it is desired to obtain the difference between two transmitter outputs. In such instances, special differential transformers have been utilized to obtain the desired readings. The above noted solutions have been somewhat awkward and costly.